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Finding the Fourth Proportional to 108.78, 149.90 and 85.49

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Solution

The fourth proportional to 108.78, 149.90 and 85.49 is: 117.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    108.78 : 149.90 = 85.49 : x
  2. Step 2: Convert to fraction form
    108.78/149.90 = 85.49/x
  3. Step 3: Cross multiply
    108.78x = 149.90 × 85.49
  4. Step 4: Simplify right side
    108.78x = 12,813.77
  5. Step 5: Solve for x
    x = 12,813.77/108.78
  6. Step 6: Final answer
    x = 117.80

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.